JP6363573B2 - Radiation source image plane distance acquisition apparatus, method and program, and radiographic image processing apparatus, method and program - Google Patents

Description

  The present invention provides a source image plane distance acquisition device that acquires a source image plane distance that is a distance between a radiation source that irradiates a subject with radiation and a detection surface of a detection unit that detects radiation transmitted through the subject, It relates to a method and a program. The present invention also relates to a radiation image processing apparatus, method, and program for performing image processing on a radiation image using a distance between the source image planes.

  Conventionally, when a radiographic image of a subject is captured by radiation transmitted through the subject, the radiation is scattered within the subject, and this scattered radiation (hereinafter referred to as scattered radiation) causes a problem that the contrast of the acquired radiographic image is lowered. is there. For this reason, at the time of radiographic image capturing, a scattered radiation removal grid (between the subject and the detection means (so that the scattered radiation is not irradiated to the detection means such as a radiation detector for detecting the radiation and acquiring the radiation image) (Hereinafter simply referred to as a grid) may be used for shooting. When imaging is performed using the grid, the radiation scattered by the subject is less likely to be applied to the detection means, so that the contrast of the radiation image can be improved.

  On the other hand, when photographing using a grid is performed, a striped pattern (grid stripe) corresponding to the grid is included in the radiation image together with the subject image, so that the image is difficult to see. For this reason, a scattered radiation removal process has been proposed in which a radiation image is taken without using a grid, and the effect of image quality improvement by removing scattered radiation by the grid is applied to the radiation image by image processing (patent). References 1 and 2). Patent Literature 1 proposes a method of performing scattered radiation removal processing based on virtual grid characteristics assuming a virtual grid. Patent Document 2 proposes a method of performing scattered radiation removal processing by estimating the body thickness of a subject.

  In recent years, so-called portable imaging using a portable radiation irradiation apparatus and a portable detection means has also been performed. Radiation irradiation devices for performing portable imaging are light enough to be carried by an operator and can be easily carried. For example, in various places such as hospital rooms and disaster sites, subjects It is possible to shoot.

JP 2014-207958 A Japanese Patent Laying-Open No. 2015-043959

  By the way, when performing image processing such as the scattered radiation removal processing described above, a distance between the radiation source image plane, that is, the distance between the radiation source and the detection surface of the detection means, that is, SID (Source to Image Distance) is required. . The SID can be easily obtained at a place where the radiation source and the detection means are installed at a fixed position, such as an imaging room. For this reason, image processing can be performed with high accuracy by using the acquired SID.

  However, when performing the above-described portable imaging, the radiation irradiation apparatus is used in a state of being held by hand, and the detection means is disposed behind the subject, so that it is difficult to obtain an accurate SID. In this case, it is conceivable to measure the SID visually and use the value for image processing. However, since the SID measured visually is not accurate, image processing cannot be performed with high accuracy. It is also conceivable to provide a sensor or the like for measuring the SID in the radiation irradiation apparatus. However, when such a sensor or the like is provided, the configuration of the apparatus becomes complicated and the cost of the apparatus increases.

  This invention is made | formed in view of the said situation, and makes it the 1st objective to enable it to acquire an exact SID.

  A second object of the present invention is to perform image processing with high accuracy using an SID.

The apparatus for acquiring a distance between image planes of a radiation source image according to the present invention includes a plurality of detection units that detect radiation emitted from a radiation source and transmitted through a subject, and at least partially overlap each other in the radiation irradiation direction. Image acquisition means for obtaining a plurality of radiation images generated by disposing at least one marker at a position detected by the means and detecting radiation transmitted through the subject and the marker by each of the plurality of detection means;
The distance between the detection surface of the first detection means located closest to the radiation source among the plurality of detection means and the detection surface of the second detection means other than the first detection means among the plurality of detection means. First information acquisition means for acquiring first information representing:
At least one marker included in the second radiographic image acquired by the second detection unit with respect to the first marker image of at least one marker included in the first radiographic image acquired by the first detection unit Second information acquisition means for acquiring second information representing the magnification of the second marker image;
And a distance calculation unit that calculates a distance between the radiation source image planes, which is a distance between the radiation source and the detection plane of the first detection unit, based on the first information and the second information. Is.

  As "detection means", in addition to the radiation detector, a part of the radiation energy is accumulated by irradiation with radiation, and then the brightness corresponding to the accumulated radiation energy is irradiated by irradiation with excitation light such as visible light or laser light. A stimulable phosphor sheet using a stimulable phosphor that emits exhausted light can be used. When the detection means is a radiation detector, the image acquisition means may acquire a radiation image represented by an image signal output from the radiation detector. When the detecting means is a stimulable phosphor sheet, radiation image information is temporarily stored and recorded on the stimulable phosphor sheet by irradiating the stimulable phosphor sheet with radiation that has passed through the subject using an imaging device, and image reading is performed. The stimulable phosphor sheet is irradiated with excitation light using an apparatus to generate stimulated emission light, and this stimulated emission light is photoelectrically converted to generate an image signal representing a radiation image. For this reason, the image acquisition means may acquire the radiation image represented by the image signal thus designated and generated.

  “Placing a plurality of detection means at least partially overlapping in the irradiation direction of the radiation image” means that the detection surfaces of the plurality of detection means are arranged perpendicular to the optical axis of the radiation emitted from the radiation source. , Which means that at least a portion is overlapped. At this time, the plurality of detection means may be in close contact with each other in an overlapping portion or may be spaced apart. In addition, “arranging at least a part in an overlapping manner” means arranging the whole of a plurality of detecting means in an overlapping manner, and arranging a part of a plurality of detecting means in an overlapping manner as in, for example, long-length photography. Including both cases.

  The “marker” has a shape that spreads in the surface direction of the detection means. For example, the line segment may have a shape that intersects the cross. In addition, the marker is made of an arbitrary material that can include a marker image that is an image of the radiographic image so that the marker image can be distinguished from the subject image. Preferably, it is made of a material such as a metal that does not pass through. The marker is preferably in close contact with the detection surface of the first detection means, but may be disposed at a position away from the detection surface of the first detection means.

  In the radiation source image surface distance acquisition device according to the present invention, when a plurality of markers are arranged, the second information acquisition unit acquires the average value of the enlargement ratio acquired for each marker as the second information. It is good also as what to do.

A radiation image processing apparatus according to the present invention includes a radiation source image surface distance acquisition device of the present invention,
An image processing unit that performs image processing on at least one of a plurality of radiation images using the distance between the source image planes acquired by the source image plane distance acquisition device is provided. is there.

  In the radiographic image processing apparatus according to the present invention, the image processing means may perform scattered radiation removal processing as image processing.

In the method for acquiring the distance between the image planes of the radiation source image according to the present invention, a plurality of detection means for detecting radiation emitted from the radiation source and transmitted through the subject are arranged so as to overlap at least partly in the radiation irradiation direction. A plurality of radiation images generated by disposing at least one marker at a position detected by the means and detecting the radiation transmitted through the subject and the marker by each of the plurality of detection means;
The distance between the detection surface of the first detection means located closest to the radiation source among the plurality of detection means and the detection surface of the second detection means other than the first detection means among the plurality of detection means. To obtain first information representing
At least one marker included in the second radiographic image acquired by the second detection unit with respect to the first marker image of at least one marker included in the first radiographic image acquired by the first detection unit Second information representing an enlargement ratio of the second marker image of
Based on the first information and the second information, the distance between the radiation source image plane, which is the distance between the radiation source and the detection surface of the first detection means, is calculated.

The radiation image processing method according to the present invention acquires the distance between the source image planes by the source image plane distance acquisition method of the present invention,
Image processing is performed on at least one of the plurality of radiation images using the distance between the source image planes.

  In addition, you may provide as a program for making a computer perform the source image surface distance acquisition method and radiographic image processing method by this invention.

  According to the present invention, the detection surface of the first detection means located closest to the radiation source among the plurality of detection means and the second detection means other than the first detection means among the plurality of detection means. First information representing the distance to the detection surface is acquired. Further, at least one included in the second radiation image acquired by the second detection unit with respect to the first marker image of at least one marker included in the first radiation image acquired by the first detection unit. Second information representing the magnification of the second marker image of the two markers is acquired. Then, the distance between the source image planes is calculated based on the first and second information. For this reason, it is possible to obtain an accurate distance between the image planes of the source image using an apparatus having a simple and inexpensive configuration without providing a sensor or the like.

  Further, by performing image processing on at least one of the plurality of radiation images using the distance between the source image planes, high-accuracy image processing using the accurate distance between the source image planes can be performed. .

1 is a schematic block diagram showing a configuration of a radiographic imaging system to which a radiation source image plane distance acquisition device and a radiographic image processing device according to an embodiment of the present invention are applied. Schematic showing the configuration of the image reading device The figure which shows schematic structure of the radiographic image processing apparatus implement | achieved by installing a radiographic image processing program in a computer The figure which shows the 1st and 2nd radiographic image The figure for demonstrating calculation of SID at the time of energy subtraction imaging | photography Block diagram showing scattered radiation removal processing A flowchart showing processing performed in the present embodiment Illustration for explaining long shooting The figure for demonstrating calculation of SID at the time of long imaging | photography

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic block diagram showing a configuration of a radiographic image capturing system to which a radiation image inter-surface distance acquisition apparatus and a radiographic image processing apparatus according to an embodiment of the present invention are applied. As shown in FIG. 1, the radiographic image capturing system according to the present embodiment captures a radiographic image of a subject H and performs various image processing including scattered radiation removal processing on the radiographic image. 1, an image reading device 2, and a computer 3 including a radiation source image plane distance acquisition device and a radiation image processing device according to the present embodiment.

  The imaging apparatus 1 irradiates two sheets of stimulable phosphor sheets IP1 and IP2 with X-rays emitted from an X-ray source 4 that is a radiation source and transmitted through a subject H, respectively, with varying energy. It is an imaging device for performing subtraction. At the time of imaging, as shown in FIG. 1, a first stimulable phosphor sheet IP1 and a second stimulable phosphor sheet IP2 are arranged in order from the side closer to the X-ray source 4, and both the sheets IP1, IP2 Between them, an X-ray energy conversion filter 5 made of a copper plate is arranged to drive the X-ray source 4. Here, the stimulable phosphor sheets IP1 and IP2 and the X-ray energy conversion filter 5 are in close contact with each other.

  In the present embodiment, a plurality of markers 6 made of a metal that does not transmit X-rays such as lead are arranged on the detection surface of the first stimulable phosphor sheet IP1. As a result, the first stimulable phosphor sheet IP1 has a low-pressure X-ray including so-called soft lines, and the second stimulable phosphor sheet IP2 has a high-pressure X-ray from which soft lines have been removed. Radiation image information is accumulated and recorded. At this time, the positional relationship of the subject H is the same between the stimulable phosphor sheet IP1 and the stimulable phosphor sheet IP2. Thereby, radiation image information in which at least part of image information of the subject H is different from each other is accumulated and recorded on the two stimulable phosphor sheets IP1 and IP2. The stimulable phosphor sheets IP1 and IP2 correspond to detection means.

  FIG. 2 is a schematic diagram showing the configuration of the image reading apparatus. As described above, among the stimulable phosphor sheets IP1 and IP2 on which the radiation image information is accumulated and recorded, the stimulable phosphor sheet IP1 is first moved in the direction of arrow Y by the endless belt 9 while the laser from the laser light source 10 is moved. The excitation light 11 that is light is deflected by the scanning mirror 12 and is subjected to main scanning in the X direction on the sheet IP1. The stimulable phosphor sheet IP1 diverges from the stimulable phosphor sheet IP1 by the amount of light corresponding to the stored and recorded radiation image information. The photostimulated emission light 13 is incident on the inside of the light guide 14 from one end face of a light guide 14 formed by molding a transparent acrylic plate, and proceeds while repeating total reflection in the light guide 14. 15 receives light. From the photomultiplier 15, an analog output signal Q1 corresponding to the light emission amount of the stimulated light emission 13, that is, indicating the radiographic image information of the subject H is output.

  The output signal Q1 is logarithmically converted by the converter 16 and further A / D converted to be converted into a digital first radiation image G1. Next, in exactly the same manner, the image information recorded on the other stimulable phosphor sheet IP2 is read out to obtain an output signal Q2, and the output signal Q2 is converted into a digital second radiation by the converter 16. It is converted into an image G2. The first and second radiation images G1 and G2 are input to the computer 3.

  A display unit 18 and an input unit 19 are connected to the computer 3. The display unit 18 includes a CRT (Cathode Ray Tube), a liquid crystal display, or the like, and assists radiation images acquired by imaging and various inputs necessary for processing performed in the computer 3. The input unit 19 includes a keyboard, a mouse, a touch panel, or the like.

  The computer 3 is installed with a source image plane distance acquisition program and a radiation image processing program of this embodiment. In addition, since the radiation source image surface distance acquisition program is included in the radiation image processing program, it is simply referred to as a radiation image processing program in the following description. In the present embodiment, the computer may be a workstation or a personal computer directly operated by an operator, or a server computer connected to them via a network. The radiation image processing program is recorded and distributed on a recording medium such as a DVD (Digital Versatile Disc) or a CD-ROM (Compact Disc Read Only Memory), and is installed in the computer from the recording medium. Alternatively, it is stored in a storage device of a server computer connected to a network or a network storage in a state where it can be accessed from the outside, and is downloaded to a computer and installed on demand.

  FIG. 3 is a diagram showing a schematic configuration of a radiographic image processing apparatus realized by installing a radiographic image processing program in the computer 3. As shown in FIG. 3, the radiation image processing apparatus includes a CPU (Central Processing Unit) 21, a memory 22, and a storage 23 as a standard computer configuration.

  The storage 23 includes a storage device such as a hard disk or SSD (Solid State Drive), and stores various information including a program for driving each unit of the imaging apparatus 1 and a radiation image processing program. In addition, a radiographic image acquired by imaging is also stored. The storage 23 also stores various tables described later.

  The memory 22 temporarily stores programs stored in the storage 23 in order to cause the CPU 21 to execute various processes. The radiological image processing program includes an image acquisition process for acquiring the first and second radiographic images G1 and G2, and a first stimulable phosphor sheet IP1 located closest to the X-ray source 4 as a process to be executed by the CPU 21. The first information acquisition process for acquiring the first information representing the distance between the detection surface and the detection surface of the second stimulable phosphor sheet IP2, the first information acquired by the first stimulable phosphor sheet IP1 Enlargement of the second marker image of the marker 6 included in the second radiation image G2 acquired by the second stimulable phosphor sheet IP2 with respect to the first marker image of the marker 6 included in the one radiation image G1 The distance between the X-ray source 4 and the detection surface of the first stimulable phosphor sheet IP1 based on the second information acquisition process for acquiring the second information representing the rate, and the first and second information. Distance calculation to calculate SID Management, defines the energy subtraction processing for the image processing, and the processed radiographic images G1, G2 for the radiation image G1, G2 of using SID.

  Then, when the CPU 21 executes these processes in accordance with the radiation image processing program, the computer 3 causes the image acquisition unit 31, the first information acquisition unit 32, the second information acquisition unit 33, the distance calculation unit 34, and the image processing. Functions as the unit 35 and the energy subtraction processing unit 36. The computer 3 may include a processor that performs an image acquisition process, a first information acquisition process, a second information acquisition process, a distance calculation process, an image process, and an energy subtraction process. Here, the stimulable phosphor sheets IP1 and IP2 correspond to first and second detection means, respectively. Moreover, the image acquisition part 31, the 1st information acquisition part 32, the 2nd information acquisition part 33, and the distance calculation part 34 comprise the source image surface distance calculation apparatus of this invention.

  The image acquisition unit 31 acquires the first and second radiation images G1 and G2 generated by the image reading device 2 and stores them in the storage 23. In addition, what is necessary is just to acquire 1st and 2nd radiographic image G1, G2 from the memory | storage device, when 1st and 2nd radiographic image G1, G2 is memorize | stored in other memory | storage devices, such as a server.

  The first information acquisition unit 32 acquires first information J1 representing the distance D between the detection surface of the first stimulable phosphor sheet IP1 and the detection surface of the second stimulable phosphor sheet IP2. Since the thickness of the first and second stimulable phosphor sheets IP1 and IP2 and the thickness of the filter 5 are known, the distance D is equal to the thickness of the first stimulable phosphor sheet IP1. Thickness is added. The 1st information acquisition part 32 acquires the 1st information J1 showing distance D by receiving the input from input part 19 by an operator. The first information J1 may be stored in the storage 23. In this case, the first information acquisition unit 32 acquires the first information J1 by reading it from the storage 23.

  The second information acquisition unit 33 uses the second stimulable phosphor sheet IP2 for the first marker image of the marker 6 included in the first radiation image G1 obtained by the first stimulable phosphor sheet IP1. 2nd information J2 showing the magnification of the 2nd marker image of the marker 6 contained in the 2nd radiation image G2 acquired by is acquired. FIG. 4 is a diagram showing the first and second radiation images G1, G2. As shown in FIG. 4, the first and second radiation images G1 and G2 include image information of the subject H and a plurality of marker images M1 and M2 of the marker 6. The marker has a shape in which a circular frame and a line segment intersecting with a cross are combined.

  Here, since the X-ray emitted from the X-ray source 4 is a cone beam, the size of the second marker image M2 included in the second radiation image G2 is the first size included in the first radiation image G1. It is larger than the size of the marker image M1. The second information acquisition unit 33 acquires the magnification K of the second marker image M2 with respect to the first marker image M1 as the second information J2. In the present embodiment, since four markers 6 are used, the first and second radiation images G1 and G2 include four first and second marker images M1 and M2, respectively. The second information acquisition unit 33 calculates four enlargement factors for each marker 6 and obtains an enlargement factor K that is a representative value such as an average value or an intermediate value of the four enlargement factors as the second information J2. The enlargement factor K is calculated by template matching between the corresponding first and second marker images M1 and M2. Further, the ratio of the diameters of the circular portions in the first and second marker images M1 and M2 in a predetermined direction may be used.

  The distance calculation unit 34 calculates the SID based on the first information J1 and the second information J2. FIG. 5 is a diagram for explaining the calculation of the SID. In FIG. 5, a broken line indicates a portion of the X-ray emitted from the X-ray source 4 that is irradiated to the marker 6. The range of the first marker image M1 is a range where the first stimulable phosphor sheet IP1 and the broken line portion of the X-ray intersect, and the range of the second marker image M2 is the second stimulable phosphor sheet. This is the range where IP2 and the broken line portion of the X-ray intersect. The magnification K, which is the second information J2 acquired by the second information acquisition unit 33, is the detection surface of the SID and the first stimulable phosphor sheet IP1, and the detection surface of the second stimulable phosphor sheet IP2. Can be expressed by the following formula (1).

K = (SID + D) / SID (1)
Therefore, the SID can be calculated by the following equation (2) using the distance D and the enlargement factor K.

SID = D / (K-1) (2)
For example, when D is 2 cm and the enlargement factor K is 1.01, the SID is 200 cm.

  The image processing unit 35 performs image processing on the first and second radiation images G1 and G2 using the SID. In the present embodiment, image processing including scattered radiation removal processing is performed. Hereinafter, the scattered radiation removal process will be described. FIG. 6 is a block diagram showing the scattered radiation removal process.

  In the present embodiment, no grid is used at the time of shooting. For this reason, the image processing unit 35 gives the first and second radiation images G1 and G2 the same effect of removing scattered rays as in the case where imaging is actually performed using a grid. Perform scattered radiation removal processing. For example, as described in Patent Document 1, the scattered radiation removal process is performed using virtual grid characteristics that are assumed to be actually used. For this reason, the image processing unit 35 acquires the virtual grid characteristic by an input from the input unit 19 by the operator. In the present embodiment, the virtual grid characteristics include the scattered radiation transmittance Ts for the virtual grid and the transmission of the primary rays that are transmitted through the subject H and irradiated to the first and second stimulable phosphor sheets IP1, IP2. The rate (primary ray transmittance) Tp. The scattered radiation transmittance Ts and the primary radiation transmittance Tp take values between 0 and 1.

  The image processing unit 35 may acquire the virtual grid characteristic by directly receiving the values of the scattered radiation transmittance Ts and the primary radiation transmittance Tp, but in the present embodiment, imaging at the time of acquisition of the radiation image By receiving an input from the condition input unit 19, the virtual grid characteristics, that is, the scattered radiation transmittance Ts and the primary radiation transmittance Tp are acquired.

  Imaging conditions include SID, imaging dose, tube voltage, radiation source target and filter material, and the type of stimulable phosphor sheet used for imaging. Here, at the time of radiographic image capturing, the type of grid to be used is generally determined according to the imaging conditions, and the scattered radiation transmittance Ts and the primary radiation transmittance Tp differ depending on the grid type. . Therefore, a table in which various shooting conditions and virtual grid characteristics are associated with each other is stored in the storage 23. Note that various imaging conditions are often determined according to the facility where the radiographic imaging system is installed. For this reason, when the shooting conditions at the time of actual shooting are unknown, the shooting conditions corresponding to the facility may be used. The image processing unit 35 refers to the table stored in the storage 23 and acquires the virtual grid characteristic based on the imaging condition input from the input unit 19.

  Then, the image processing unit 35 calculates a primary line image and a scattered ray image based on the following formulas (3) and (4) from the subject thickness distribution T (x, y) in the radiation images G1 and G2, Based on the calculated primary ray image and scattered ray image, the scattered ray content distribution S (x, y) is calculated based on the equation (5).

Icp (x, y) = Io (x, y) × exp (-μ × T (x, y)) (3)
Ics (x, y) = Io (x, y) * Sσ (T (x, y)) (4)
S (x, y) = Ics (x, y) / (Ics (x, y) + Icp (x, y)) (5)
Here, (x, y) is the coordinates of the pixel position of the projection image Gi, Icp (x, y) is the primary line image at the pixel position (x, y), and Ics (x, y) is the pixel position (x, y). ) Is a scattered radiation image, Io (x, y) is an incident dose to the subject surface at the pixel position (x, y), μ is a linear attenuation coefficient of the subject H, and Sσ (T (x, y)) is a pixel position ( This is a convolution kernel representing the scattering characteristic according to the subject thickness in x, y).

  The subject thickness distribution T (x, y) assumes that the luminance distributions in the first and second radiation images G1 and G2 substantially match the subject thickness distribution. What is necessary is just to calculate by converting the pixel value of radiation image G1, G2 into thickness by a linear attenuation coefficient value. Alternatively, the thickness of the subject H may be measured using a sensor or the like, or approximated by a model such as a cube or an elliptic cylinder.

  The incident dose Io (x, y) is an X-ray dose irradiated to the stimulable phosphor sheets IP1 and IP2 when it is assumed that the subject H does not exist, and changes according to the SID, tube voltage, and mAs value. To do. In the present embodiment, a table in which various SIDs, tube voltages and mAs values are associated with incident doses is stored in the storage 23, and the incident dose Io ( x, y) is obtained.

  * In the formula (4) is an operator representing a convolution operation. Furthermore, Sσ (T (x, y)) can be experimentally determined according to the imaging conditions. In the present embodiment, a table in which various shooting conditions are associated with Sσ (T (x, y)) is stored in the storage 23, and Sσ (T (x, y) is referenced with reference to this table from the shooting conditions. )).

  Then, the image processing unit 35 converts the radiation images G1 and G2 from the scattered radiation transmittance Ts and the primary radiation transmittance Tp, which are virtual grid characteristics, and the scattered radiation content distribution S (x, y). (X, y) is calculated by the following equation (6). Furthermore, the image processing unit 35 multiplies the pixel value of each pixel of the first and second radiation images G1 and G2 by the conversion coefficient R (x, y) by the following equation (7), thereby Then, the scattered radiation components are removed from the second radiographic images G1 and G2 to obtain first and second processed radiographic images.

R (x, y) = S (x, y) × Ts + (1-S (x, y)) × Tp (6)
Gs (x, y) = R (x, y) × G (x, y) (7)
Note that the first and second radiation images G1 and G2 may be decomposed into a plurality of frequency bands, and conversion coefficient calculation and conversion coefficient multiplication may be performed for each frequency band. In this case, the processed first and second radiation images Gs1 and Gs2 are obtained by frequency-combining the projection images of the respective frequency bands multiplied by the conversion coefficient.

  The image processing unit 35 may perform other image processing such as gradation correction processing, density correction processing, and frequency enhancement processing on the processed radiographic images Gs1 and Gs2.

  The energy subtraction processing unit 36 performs weighted subtraction processing between corresponding pixels of the processed radiographic images Gs1 and Gs2. Thereby, the energy subtraction processing unit 36 generates a soft part image in which only the soft part of the subject H is extracted and a bone part image in which only the bone part is extracted. At this time, alignment of the processed radiographic images Gs1 and Gs2 is performed using the marker images M1 and M2. That is, at least one of the processed radiographic images Gs1 and Gs2 may be translated, rotated, and enlarged / reduced so that the marker images M1 and M2 coincide with each other, and the processed radiographic images Gs1 and Gs2 are aligned. .

  Next, processing performed in the present embodiment will be described. FIG. 7 is a flowchart showing processing performed in the present embodiment. First, the image acquisition unit 31 acquires the first and second radiation images G1, G2 generated from the first and second stimulable phosphor sheets IP1, IP2 by the image reading device 2 (step ST1). Next, the first information acquisition unit 32 acquires first information J1 representing the distance D between the detection surface of the first stimulable phosphor sheet IP1 and the detection surface of the second stimulable phosphor sheet IP2. (Step ST2). Furthermore, the second information acquisition unit 33 performs the second storage phosphor with respect to the first marker image of the marker 6 included in the first radiation image G1 acquired by the first storage phosphor sheet IP1. Second information J2 representing the magnification K of the second marker image of the marker 6 included in the second radiation image G2 acquired by the sheet IP2 is acquired (step ST3).

  Then, the distance calculation unit 34 calculates the SID based on the first information J1 and the second information J2 (step ST4). Next, the image processing unit 35 performs image processing including scattered radiation removal processing on the first and second radiographic images G1 and G2 to obtain processed radiographic images Gs1 and Gs2 (step ST5). Further, the energy subtraction processing unit 36 performs energy subtraction processing on the processed radiographic images Gs1 and Gs2 to generate a soft part image in which only the soft part of the subject H is extracted and a bone part image in which only the bone part is extracted. (Step ST6), the process ends. The soft part image and the bone part image are displayed on the display unit 18 for diagnosis.

  Thus, in this embodiment, since the SID is calculated based on the first information J1 and the second information J2, an accurate SID can be obtained using a simple and inexpensive device without providing a sensor or the like. Can be obtained.

  Further, by performing image processing on the plurality of first and second radiation images G1 and G2 using the acquired SID, it is possible to perform high-precision image processing using an accurate SID.

  In the above embodiment, the radiation image of the subject H is acquired by superimposing the two stimulable phosphor sheets IP1 and IP2 in order to perform the energy subtraction process, but the entire bone of the subject H (the entire spine) The SID can also be calculated using the technique of the present application using a radiographic image obtained by long imaging of a long region such as the entire leg or all legs (all legs). FIG. 8 is a diagram for explaining long shooting. In FIG. 8, three stimulable phosphor sheets IP1, IP2, and IP3 are used. As shown in FIG. 8, at the time of long photographing, the three stimulable phosphor sheets IP1, IP2, and IP3 are arranged so as to partially overlap each other. Of the stimulable phosphor sheets IP1 and IP3 on the side close to the X-ray source 4, the marker 6 is disposed on the surface of the stimulable phosphor sheet IP1. In the long photographing, radiographic image information of the whole body of the subject H is accumulated and recorded on three arranged phosphorescent phosphor sheets IP1, IP2, and IP3, and radiographic images are respectively obtained from the stimulable phosphor sheets IP1, IP2, and IP3. Information is read out to generate radiographic images G1, G2, and G3, and the generated radiographic images G1, G2, and G3 are connected to generate a long radiographic image GL.

  Here, among the radiographic images G1, G2, and G3 acquired by the long imaging, the overlapping portions of the radiographic images G1 and G2 include the marker images M1 and M2 of the marker 6, respectively. FIG. 9 is a diagram for explaining the calculation of the SID during long shooting. In FIG. 9, a broken line indicates a portion of the X-ray emitted from the X-ray source 4 that passes through the marker 6. The range of the first marker image M1 is a range where the first stimulable phosphor sheet IP1 and the broken line portion of the X-ray intersect, and the range of the second marker image M2 is the second stimulable phosphor sheet. This is the range where IP2 and the broken line portion of the X-ray intersect. As shown in FIG. 9, the relationship between the magnification K of the second marker image M2 with respect to the first marker image M1, the distance D between the detection surfaces of the stimulable phosphor sheets IP1 and IP2, and the SID is shown in FIG. Is the same. Therefore, even when long imaging is performed, the first information acquisition unit 32 acquires the distance D between the detection surfaces of the stimulable phosphor sheets IP1 and IP2 as the first information J1, and acquires the second information. By obtaining the magnification K of the second marker image M2 with respect to the first marker image M1 as the second information J2 by the unit 33, the distance calculating unit 34 calculates the SID using the above equation (2). be able to.

  In the above-described embodiment, a radiation image is acquired by irradiating the stimulable phosphor sheet with X-rays transmitted through the subject H and reading out radiation image information from the stimulable phosphor sheet in the image reading device 2. Yes. However, instead of the stimulable phosphor sheet, a radiation image may be acquired using a radiation detector.

  The radiation detector can repeatedly perform recording and reading of a radiation image, and may use a so-called direct type radiation detector that directly receives radiation to generate electric charge, A so-called indirect radiation detector that converts the visible light into a charge signal once may be used. As a radiation image signal reading method, a radiation image signal is read by turning on and off a TFT (thin film transistor) switch, or a radiation image signal by irradiating reading light. Although it is desirable to use a so-called optical readout system in which is read out, the present invention is not limited to this, and other types may be used.

  Even when a radiation detector is used, the SID can be calculated as in the above embodiment. Here, instead of the first and second stimulable phosphor sheets IP1 and IP2 in the embodiment, the first and second radiation detectors DR1 and DR2 are used, and the first and second radiation detectors are used. It is assumed that first and second radiation images G1 and G2 are acquired from DR1 and DR2, respectively. The first information acquisition unit 32 acquires first information J1 representing the distance between the detection surface of the first radiation detector DR1 and the detection surface of the second radiation detector DR2. Even in this case, since the thicknesses of the first and second radiation detectors DR1 and DR2 and the thickness of the filter 5 are known, the distance D is equal to the thickness of the first radiation detector DR1 and the thickness of the filter 5. Will be added. On the other hand, the second information acquisition unit 33 is acquired by the second radiation detector DR2 with respect to the first marker image of the marker 6 included in the first radiation image G1 acquired by the first radiation detector DR1. The second information J2 representing the enlargement ratio of the second marker image of the marker 6 included in the second radiation image G2 is acquired. And the distance calculation part 34 can calculate SID based on the 1st information J1 and the 2nd information J2 by said Formula (2).

  Moreover, in the said embodiment, although the some marker 6 is used, you may make it use only one marker 6. FIG.

  Moreover, in the said embodiment, although the marker 6 which consists of a metal which does not permeate | transmit X-rays is used, if a marker image can be included in a radiographic image so that it can distinguish from a to-be-photographed image, it will permeate | transmit X-rays. You may use the marker 6 which consists of materials, such as a metal or resin.

  Moreover, in the said embodiment, although the marker 6 is closely_contact | adhered to the storage phosphor sheet | seat near the X-ray source 4, you may arrange | position in the position away from the storage phosphor sheet | seat. For example, it may be placed on the subject H.

  Further, in the above-described embodiment, imaging is performed such that two stimulable phosphor sheets overlap with the optical axis of the X-ray, but three or more stimulable phosphor sheets are arranged so as to overlap. Even when shooting is performed, the SID can be calculated in the same manner as in the above embodiment. In this case, the distance D between the detection surface of the stimulable phosphor sheet closest to the X-ray source and the detection surface of any of the second and subsequent stimulable phosphor sheets from the side close to the X-ray source, and X For the marker image included in the radiation image acquired from the stimulable phosphor sheet closest to the radiation source, the magnification K of the marker image included in the radiation image acquired from the stimulable phosphor sheet used to acquire the distance D is What is necessary is just to acquire and use for calculation of SID.

  Moreover, in the said embodiment, although the method described in patent document 1 is used as a scattered-radiation removal process, arbitrary methods, such as the method described in patent document 2, can be used.

  Moreover, in the said embodiment, although the scattered radiation removal process is performed as a process using SID, you may make it perform the other image process using SID.

DESCRIPTION OF SYMBOLS 1 Imaging device 2 Image reader 3 Computer 4 X-ray source 5 X-ray energy conversion filter 6 Marker 21 CPU
22 memory 23 storage 31 image acquisition unit 32 first information acquisition unit 33 second information acquisition unit 34 distance calculation unit 35 image processing unit 36 energy subtraction processing unit

Claims (8)

A plurality of detection means for detecting radiation emitted from a radiation source and transmitted through a subject are arranged so as to overlap at least partly in the radiation irradiation direction, and at least one marker is located at a position detected by the plurality of detection means An image acquisition means for acquiring a plurality of radiation images generated by detecting the radiation transmitted through the subject and the marker by each of the plurality of detection means;
The detection surface of the first detection means that is closest to the radiation source among the plurality of detection means, and the detection of the second detection means other than the first detection means of the plurality of detection means First information acquisition means for acquiring first information representing a distance to the surface;
The first radiation image acquired by the second detection means with respect to the first marker image of the at least one marker included in the first radiation image acquired by the first detection means. Second information acquisition means for acquiring second information representing the magnification of the second marker image of at least one marker;
Distance calculating means for calculating a distance between the source image planes, which is a distance between the radiation source and the detection surface of the first detection means, based on the first information and the second information; An apparatus for acquiring a distance between image planes of a source image.   The distance between the source image planes according to claim 1, wherein, when a plurality of the markers are arranged, the second information acquisition unit acquires an average value of the enlargement ratio acquired for each marker as the second information. Acquisition device. The source image surface distance acquisition device according to claim 1 or 2,
Image processing means for performing image processing on at least one of the plurality of radiation images using the distance between the source image planes acquired by the source image plane distance acquisition apparatus. Radiation image processing device.   The radiation image processing apparatus according to claim 3, wherein the image processing unit performs scattered radiation removal processing as the image processing. A plurality of detection means for detecting radiation emitted from a radiation source and transmitted through a subject are arranged so as to overlap at least partly in the radiation irradiation direction, and at least one marker is located at a position detected by the plurality of detection means A plurality of radiation images generated by detecting the radiation transmitted through the subject and the marker by each of the plurality of detection means,
The detection surface of the first detection means that is closest to the radiation source among the plurality of detection means, and the detection of the second detection means other than the first detection means of the plurality of detection means Obtaining first information representing the distance to the surface;
The first radiation image acquired by the second detection means with respect to the first marker image of the at least one marker included in the first radiation image acquired by the first detection means. Obtaining second information representing an enlargement ratio of a second marker image of at least one marker;
Based on the first information and the second information, a source image plane distance, which is a distance between the radiation source and a detection plane of the first detection means, is calculated. Inter-surface distance acquisition method. A source image plane distance is acquired by the source image plane distance acquisition method according to claim 5,
A radiation image processing method, wherein image processing is performed on at least one of the plurality of radiation images using the distance between the radiation source image planes. A plurality of detection means for detecting radiation emitted from a radiation source and transmitted through a subject are arranged so as to overlap at least partly in the radiation irradiation direction, and at least one marker is located at a position detected by the plurality of detection means Obtaining a plurality of radiation images generated by detecting the radiation transmitted through the subject and the marker by each of the plurality of detection means;
The detection surface of the first detection means that is closest to the radiation source among the plurality of detection means, and the detection of the second detection means other than the first detection means of the plurality of detection means Obtaining first information representing a distance to the surface;
The first radiation image acquired by the second detection means with respect to the first marker image of the at least one marker included in the first radiation image acquired by the first detection means. Obtaining second information representing an enlargement ratio of a second marker image of at least one marker;
Causing the computer to execute a procedure for calculating a distance between the radiation source image planes, which is a distance between the radiation source and the detection plane of the first detection unit, based on the first information and the second information. A program for acquiring the distance between the image planes of the source images. A procedure for acquiring a distance between source image planes by a program for acquiring a distance between source image planes according to claim 7;
A radiation image processing program causing a computer to execute a procedure for performing image processing on at least one of the plurality of radiation images using the distance between the source image planes.